Self lubricating submersible pumping system

ABSTRACT

A lubrication technique for one or more components used in the production of subterranean fluids. The technique comprises the separation of particulates from a produced fluid having lubricating ability. Following separation of the particulate matter, the lubricating fluid is directed to specific areas, such as bearing surfaces within a submersible pump, to facilitate continued operation of the overall system.

FIELD OF THE INVENTION

[0001] The present invention relates generally to the production of hydrocarbon-based fluids from subterranean locations, and particularly to a technique for lubricating components in a pumping system utilized in producing such fluids from beneath the earth's surface.

BACKGROUND OF THE INVENTION

[0002] The production of fluids from subterranean reservoirs is accomplished by a variety of methods. For example, oil is commonly produced to the surface of the earth by drilling a wellbore into a formation containing the desired fluid. Subsequently, an artificial lift mechanism is deployed within the wellbore, and oil is produced to the surface of the earth or to another storage location. The artificial lift is commonly provided by pumping systems, such as electric submersible pumping systems. When using such a system, a submersible pump powered by a submersible motor is moved into the wellbore until at least partially submersed in the fluid that has flowed into the wellbore from the surrounding formation. The pump is then powered to move the fluid, e.g. oil, from the wellbore to a desired location.

[0003] In some wellbore environments, the fluid contains particulates, such as sand, that can be detrimental to the operation of certain system components, such as the submersible pump. For example, the abrasive particles can wear on certain surfaces, such as bearing surfaces, within the submersible pump. In some applications, sand separators have been disposed upstream of the submersible pump to separate sand from the oil before the oil is drawn into the submersible pump. The removal of sand decreases the pump wear. However, the removal of sand decreases efficiency and can create substantial amounts of sand within the wellbore. This sand either accumulates in the wellbore or must somehow be removed.

SUMMARY OF THE INVENTION

[0004] The present invention provides an efficient technique for reducing wear on certain component surfaces otherwise susceptible to wear during the pumping of a fluid containing particulate matter. The technique separates particulates from at least a portion of the fluid, e.g. oil, produced by the submersible pump to create a supply of lubricant having substantially lower particulate content. This modified fluid is directed back to a desired component, such as the submersible pump, to provide a better quality lubricant for specific surfaces, such as bearing surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

[0006]FIG. 1 is a front elevational view of an exemplary fluid production device incorporating a lubrication system, according to one embodiment of the present invention;

[0007]FIG. 2 is a front elevational of a portion of the device illustrated in FIG. 1 with a particulate separator illustrated in partial-cutaway form;

[0008]FIG. 3 is a schematic illustration of an exemplary particulate separator shown in a cross-section taken generally along its axis; and

[0009]FIG. 4 is a cross-sectional view of a portion of an exemplary submersible pump taken generally along its axis.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0010] Referring generally to FIG. 1, an artificial lift mechanism 10 is illustrated at a subterranean location 12. In this specific embodiment, artificial lift mechanism 10 comprises an electric submersible pumping system. However, it should be noted that a variety of artificial lift mechanisms can be utilized, and the number, type and arrangement of components within a given artificial lift mechanism may vary substantially. For purposes of explanation, artificial lift mechanism 10 will be described as an electric submersible pumping system having the exemplary components illustrated in FIG. 1 and described below.

[0011] As illustrated in both FIGS. 1 and 2, electric submersible pumping system 10 is deployed in a wellbore environment in which a wellbore 14 is drilled into a subterranean formation 16 containing a hydrocarbon-based fluid, such as oil 18. In the example illustrated, wellbore 14 is lined with a wellbore casing 20 having a plurality of openings 22, sometimes referred to as perforations, through which oil 18 flows from formation 16 into wellbore 14. Wellbore casing 20 extends upwardly through wellbore 14 to a wellhead 24 that may be disposed, for example, at a surface 26 of the earth.

[0012] The exemplary electric submersible pumping system 10 comprises a submersible motor 28 powered by an electrical power cable 30. System 10 further comprises a motor protector 32 and a submersible pump 34 having a pump intake 36. In this example, submersible pump 34 comprises a centrifugal style pump. Furthermore, submersible pump 34, motor protector 32 and submersible motor 28 are illustrated as coupled to each other for purposes of explanation only. Additional motors, pumps or other components can be inserted or exchanged for a given application.

[0013] Electric submersible pumping system 10 further comprises a particulate separator 38 disposed downstream from submersible pump 34. Particulate separator 38 is designed to separate particles, such as sand, from at least a portion of the produced fluid, e.g. oil 18. System 10 typically is coupled to a deployment system 40 by, for example, a connector 42. Deployment system 40 is representative of a variety of available deployment systems, such as production tubing, coiled tubing and cable systems. In the specific design illustrated, a production tubing 44 is used to suspend system 10 within wellbore 14 and to direct the flow of fluid produced by submersible pump 34 to, for example, surface 26 of the earth.

[0014] During operation of electric submersible pumping system 10, submersible motor 28 rotates a pump shaft 45 (see FIG. 2) to create a pumping action, as known to those of ordinary skill in the art. A produced fluid, such as oil 18, is drawn into pump intake 36, directed through submersible pump 34 and into particulate separator 38. This produced fluid, represented by arrows 46, ultimately is produced to a desired location by, for example, production tubing 44. However, at least a portion of this fluid flow 46 undergoes a separation process to remove particulate matter. Once particulate matter is removed, a modified fluid 48 results. (See arrow representing modified fluid 48 in FIG. 2). Because the particulate matter is removed, the modified fluid 48 has better lubrication qualities and can be directed to desired areas that benefit from those qualities.

[0015] One exemplary separation mechanism 50 comprises a hydrocyclone separator disposed within particulate separator 48 (see FIG. 2). Hydrocyclone separator 50 is one type of centrifugal separator that receives a portion of the produced fluid 46 and separates particulate matter to form modified fluid 48. The hydrocyclone separator 50 is fluidically coupled to a separator shaft 52 which, in turn, is coupled to pump shaft 45.

[0016] A passageway 54 directs modified fluid 48 from the hydrocyclone separator 50 to one or more desired locations, such as specific locations within submersible pump 34. In the embodiment illustrated, passageway 54 is disposed through separator shaft 52 and pump shaft 45 to form a flow path for modified fluid 48. Separator 38 is designed to create a pressure on modified fluid 48, as it passes through passageway 54, that is greater than the ambient pressure surrounding electric submersible pumping system 10.

[0017] A variety of separation mechanisms 50 can be utilized to create modified fluid 48, as illustrated schematically in FIG. 3. In this generic example, the produced fluid 46 from submersible pump 34 is directed into particulate separator 38, as indicated in FIG. 3. The fluid 46 flows into a circulating blade 58 mounted to separator shaft 52. Rotating blade 58 imparts a rotation to fluid 46 such that centrifugal force causes the heavier particulates to move outwardly to a surrounding wall 60. The particulates can be redirected, for example, back into the primary production flow and ultimately through tubing 44, or they can be directed to another location.

[0018] The fluid from which the particulates have been removed, i.e. modified fluid 48, is directed downwardly through passageway 54 which is initiated in separator shaft 52. Depending on the design of separator mechanism 50, the higher pressure of modified fluid 48 relative to ambient can be created by, for example, a constriction 62 formed along wall 60. However, the particular pressurizing mechanism may vary depending on the type of separation mechanism 50 used in creating modified fluid 48.

[0019] In the example illustrated in FIG. 4, modified fluid 48 is directed along passageway 54 from separator shaft 52 into submersible pump shaft 45. The fluid 48 flows along passageway 54 to a plurality of desired lubrication regions 64. In this example, lubrication regions 64 generally comprise a plurality of bearings, such as radial bearings 66 or thrust bearing system 68. Thrust bearing system 68 typically has a thrust bearing 70 and a rotor 72. The exemplary passageway 54 comprises an axial passage segment 74 and a plurality of transverse passage segments 76 disposed to direct flow of modified fluid 48 to the desired lubrication regions, e.g. bearings 66 and 68.

[0020] It should be noted that desired lubrication regions 64 may be at non-bearing locations or in other types of submersible pumping system components. Additionally, the illustrated bearing 66 and 68 are merely representative and can comprise a variety of other types of bearings. For example, the bearings can be stage radial bearings, thrust bearings, including pivoted pad thrust bearings, tilted pad bearings and/or ceramic bearings, as well as magnetic coupling bearings. Additionally, the bearings can be deployed within bearing housings that have appropriate openings to permit the flowthrough of production fluid 46. In the embodiment illustrated in FIG. 4, for example, flow paths 78 are formed through or along thrust bearing system 68 to facilitate continued flow through submersible pump 34 via a plurality of impellers 80 and diffusers 82, as known to those of ordinary skill in the art.

[0021] Simultaneously, the modified fluid 48 is directed through appropriate transverse passages 64 proximate the corresponding bearing surfaces requiring lubrication. In a typical application, the modified fluid 48 is under a higher pressure that forces the modified fluid along the desired bearing surfaces and out into the production flow.

[0022] In some applications, it may be advantageous to provide a supplemental or alternative supply of modified fluid 48. For example, the modified fluid may be supplied from a downhole fluid purifier or sand separator disposed at a separate location. Additionally, a clean supply of lubricant can be provided through appropriate tubing from other locations.

[0023] It should be understood that the foregoing description is of exemplary embodiments of this invention, and that the invention is not limited to the specific forms shown. For example, a variety of pumping systems can benefit from the type of lubricating technique discussed herein. A wide variety of pump styles, currently available or potentially developed in the future, may benefit from the lubrication of specific regions. Additionally, the fluid can be directed along other types of passageways if the pump or other lubricated component does not comprise a shaft. These and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims. 

What is claimed is:
 1. A lubrication system, comprising: an electric submersible pumping system having a submersible pump and a particulate separator disposed downstream of the submersible pump, the submersible pump comprising a shaft with an internal lubrication flow path positioned to receive a fluid from the particulate separator subsequent to separation of particulates:from the fluid.
 2. The lubrication system as recited in claim 1, wherein the submersible pump comprises a plurality of bearing regions, and the internal lubrication flow path extends to the plurality of bearing regions.
 3. The lubrication system as recited in claim 1, wherein the particulate separator comprises a centrifugal sand separator.
 4. The lubrication system as recited in claim 1, wherein the electric submersible pumping system comprises an electric motor to drive the submersible pump and the particulate separator.,
 5. The lubrication system as recited in claim 1, wherein the internal lubrication flow path comprises an axial passage disposed along an axis of the shaft and a plurality of transverse passages extending from the axial passage to the exterior of the shaft.
 6. The lubrication system as recited in claim 1, wherein the particulate separator comprises a hydrocyclone separator.
 7. The lubrication system as recited in claim 1, wherein the fluid is obtained from a primary fluid flow produced by the submersible pump.
 8. A method of lubricating a wellbore component with a formation fluid, comprising: producing a fluid from a wellbore formed in a subterranean formation; within the wellbore, separating particulates from at least a portion of the fluid to obtain a modified fluid; and directing the modified fluid to a desired lubrication region of a wellbore component.
 9. The method as recited in claim 8, wherein producing comprises pumping the fluid with a submersible pump.
 10. The method as recited in claim 9, wherein separating comprises separating the particulates downstream of the submersible pump.
 11. The method as recited in claim 10, wherein directing comprises routing the modified fluid to a plurality of regions within the submersible pump.
 12. The method as recited in claim 11, wherein pumping comprises pumping the fluid with a submersible, centrifugal pump having a pump shaft.
 13. The method as recited in claim 12, wherein routing comprises moving the modified fluid through a passageway formed in the pump shaft.
 14. The method as recited in claim 13, wherein moving comprises lubricating a plurality of bearings within the submersible pump.
 15. The method as recited in claim 11, wherein separating comprises utilizing a hydrocyclone to obtain the modified fluid.
 16. The method as recited in claim 11, further comprising maintaining the modified fluid at a pressure higher than the ambient pressure.
 17. A method of lubricating a submersible pump used in a wellbore application, comprising: pumping an oil-based fluid with a submersible pump driven by a pump shaft; separating particulates from a portion of the oil-based fluid subsequent to pumping to form a modified fluid; and directing the modified fluid through a passageway in the pump shaft to desired lubrication regions.
 18. The method as recited in claim 17, wherein directing comprises directing the modified fluid to a plurality of bearings in the submersible pump.
 19. The method as recited in claim 18, wherein separating comprises circulating the portion in a hydrocyclone separator.
 20. The method as recited in claim 17, wherein directing comprises moving the modified fluid along an axial passageway in the shaft to a transverse passageway proximate a bearing.
 21. The method as recited in claim 17, wherein pumping comprises powering the submersible pump via a submersible motor.
 22. The method as recited in claim 17, further comprising maintaining the modified fluid at an internal pressure within the passageway, the internal pressure being greater than ambient pressure.
 23. The method as recited in claim 22, wherein directing comprises directing the modified fluid to a plurality of bearings in the submersible pump.
 24. A submersible-pumping system, comprising: a submersible motor; a submersible pump powered by the motor; a separator disposed downstream of the submersible pump, the separator being able to separate particulates from at least a portion of the fluid produced by the submersible pump to create a modified fluid; and a lubrication system disposed to direct modified fluid from the separator to a select region of the submersible pump.
 25. The submersible pumping system as recited in claim, 24, wherein the submersible pump is a centrifugal pump having a pump shaft.
 26. The submersible pumping system as recited in claim 25, wherein the lubrication system comprises a passageway in the pump shaft.
 27. The submersible pumping system as recited in claim 26, wherein the passageway comprises an axial portion and a plurality of transverse portions.
 28. The submersible pumping system as recited in claim 27, wherein the submersible pump comprises a plurality of bearing areas positioned to receive modified fluid directed through the plurality of transverse portions.
 29. The submersible pumping system as recited in claim 26, wherein the modified fluid in the passageway is maintained at a pressure higher than ambient pressure.
 30. The submersible pumping system as recited in claim 26, wherein the separator comprises a hydrocyclone separator.
 31. A system for lubricating a submersible pump in a wellbore application, comprising: means for pumping an oil-based fluid with a submersible pump driven by a pump shaft; means for separating particulates from a portion of the oil-based fluid subsequent to pumping to form a modified fluid; and means for directing the modified fluid through a passageway in the pump shaft to desired lubrication regions.
 32. The system as recited in claim 31, wherein the means for pumping comprises a centrifugal pump.
 33. The system as recited in claim 31, wherein the means for separating comprises a particulate separator located downstream of the submersible pump.
 34. The system as recited in claim 31, wherein the means for directing comprises a plurality of passageway sections positioned to deliver modified fluid to a plurality of bearings. 